You have a strange view of libertarianism if you think he would need to build his floating city without money to be truly following it. I thought libertarianism is about the right to do whatever you want with your money?

Such a project would necessarily take a large amount of resources, regardless of the intentions behind it. In practical terms, that means money. I don't see why that's strange.

Now if you think it's just going to be an amusement park, that's a separate issue. I agree that there's at least a significant risk of that. It would be a waste of a good idea.